I've got a miss and pop in my car that I seem to have trouble tracking down, just replaced all plugs with TR-55's @ .045 gap, and began missing again after about 5-10 minutes. The O2's have only been on about a month and were replaced about a month after the LT install. Now about a week ago, it was running great, but then I hit something in the road that put a quarter size hole in one of the primaries right before the collector and of course before the O2. It started missing within minutes, so I pulled in a muffler shop who welded up the hole. Ever since I have been trying to pinpoint this miss. I at first thought the plugs had fouled, so I replaced them, reset the PCM with battery unplugged for a few hours, then ran up the street and it started missing within minutes accompanied by the popping in the exhuast. I just got a plug wire tester to track down the problem.

Question is this, does the car have to be running to test spark, or can I pull the fuel pump fuse and just crank the engine to test, so I dont have to deal with the hot headers?

 

You can pull the fuel pump fuse, but beware the car might still fire briefly due to residual fuel pressure. If something hit my header hard enough to puncture it, I'd be looking for a leak someplace else, too. Could have bent the header, yanked it off the head a bit, etc.

 

Thats what I was thinking. It wouldn't be a bad idea to inspect the rest of the setup and make sure there is no other visible damage.

 

Yeah I checked that, the bolts are still tight, no other signs of damage that I could find, I had hit it pulling out of a parking lot, it was like a sewer grate that was sticking up, so I wasnt going but a few mph, but I did seem to hit the corner of the grate. I did notice however the next day that side's O2 extention had hit the ground and one of the wires had worn thru the insulation, but was still intact, could this cause the problem as well?

 

If it was grounding out on the header or something else it could make it run bad and throw a code. It happened to me at the track, I couldnt get the car to idle anymore, and it was throwing codes (never saw which ones). The next day I was looking through the car and saw the o2 wires had burned on the header and grounded.

 

I'll check how thin that wire is, might have to cut and reconnect the wire if its worn too thin. Not getting any engine codes either. I guess I'll check the plug wires and plugs again, then repair that O2 extention wire, then scan it to see what its doing if that dont work. I'll post tonight with the results.

 

Do you have the equipment to log your car? That would be your best option. Are all the plugs fouling? What cylinders are misfiring?

 

I have DataMaster, just have to use the old PC in the garage and hook it up to that to scan. I'm not sure which side or plugs are fouling, its a 95 so its OBDI, so it wont tell me which cylinder is misfiring. Will be able to check it out here in a little bit.

 

The plugs will tell you everything you need to know. Scan the car and check the O2 voltages to make sure they are fluctuating and acting correctly. Also, check your fuel trims on both sides.

 

Didnt get a chance to pull the plugs but I used the spark tester, but didnt like it very well, it is the kind you have to hold in place with a probe, and while cranking the engine with fuel pump relay disconnected it just barely lit up, even on the coil and even after putting on a brand new wire. Although the tester I'm using is one of these http://www.partsamerica.com/ProductD...artnumber=3810 style, so it had to be held on the wire connection while clipped on the plug, didnt light up very bright.

Once it got dark I shut the garage door and turned the lights out, making it pitch black and ran the car looking for sparks, I couldnt see anything at all.

Fixed the O2 harness wire, then hooked up to the DataMaster, once it hit closed loop it read around 122 on both of the Long term trims and from 118-125 on right and 120-131 on the left side at idle. O2 readings read from about 100-850 at idle. Any ideas/suggestions to check out tomorrow?

 

Values seem pretty normal.

 

So should I assume it to be a plug wire or bad plug?

 

You could always get a voltmeter and check the resistance value of the wires to see if any of them are showing very high resistance readings. Also, you could pull the plugs and inspect their condition.

 

Well apparently I was using the spark tester wrong, looked at the directions, got it working right. All 8 wires sparked great on the tester while cranking, so its not the wires. Ran some Seafoam thru the engine at the TB vaccuum line (**it kept dying as soon as I tried to pull the brake booster line, thats not right is it?**) , shut it off, then soaked the inside of the intake manifold with Deep Creek to clean out some of the carbon deposits as well. Still used the same spark plugs since was using the Seafoam. It was running a little better, at first, let it run about 1500-2000 rpm while it cleared the smoke screen out, then let it idle while I cleaned up the garage.
Took it out for a little spirited run, still noticing a slight occasional miss, but didnt seem as bad as before, till I got about a mile down the road then it started running rough, especially at higher rpms. Almost sounded like a new exhaust leak, maybe coming from the slip fit tube, so I am going to get a hose clamp tomorrow to try to seal the slip tube on the Hookers to see if that cures the exhaust leak.
Once I parked it, and got out, it sounded terrible, the top of the engine was ticking very loud, not sure if it is a bad injector, loose rocker arm, or bad lifter. How can I tell what is making the noise? I assume whatever it is has something to do with the missing/running rough problem, how can I determine what the ticking is so I can quit playing the guessing game and get my car back on the road?
Any suggestions would be greatly appreciated, I am tired of not driving my car!

 

I think I'm going to put in the new spark plugs, then see if I can make sure the stock rockers are adjusted correctly. I've heard of 2 ways to do this, correct me if I'm wrong.
1. Running method - With valve covers off and engine running, tighten the rocker making the ticking until it stops (zero lash) then turn about 1/4 or 1/2 turn more.
2. With engine off, rotate crank until the rocker to be adjusted is with the valve fully closed, then adjust until there is no more up/down movement or turning of the pushrod (zero lash) then 1/4 or 1/2 turn more.

Is this correct? Any other suggestions before I try this this afternoon?